Technical Abstract:
Many species of Thinopyrum and Leymus are known to be highly salt tolerant. Salinity tolerance in diploid Thinopyrum elongatum, thus all polyploid Thinopyrum species too, is controlled by genes on different chromosomes. Some candidate genes, including genes for peroxidase precursor, for salinity tolerance had been identified through a microarray study on two wheat translocation lines involving chromatins from Thinopyrum junceum and Aegilops speltoides. In addition to toxic effects, salt and heavy-metal stresses can also induce oxidative stress with the formation and accumulation of reactive oxygen species (ROS). Antioxidant enzyme activities of superoxidase dismutase, catalase, peroxidase, ascorbate peroxidase and glutathione reductase appeared to be responsible for the higher tolerance to abiotic stresses in plants. Bacterial artificial chromosome (BAC) genomic DNA library representing about 6.1 haploid genome equivalents of tetraploid Leymus had been previously developed. By screening the entire BAC library with designed Overgo primers, 11 BAC clones that might contain homoeologous genes controlling salinity tolerance or being affected by salt stress had subsequently been selected and sequenced. Contig sequences of two BAC clones targeting the peroxidase precursor will be analyzed to find polymorphisms among the orthologous genes from various plant species. Further research may lead to the development of molecular markers for marker-assisted selection in breeding programs aiming at improving tolerance to abiotic stresses.